1. Field of the Invention
The present invention relates to a thin film transistor and an organic light emitting device including the thin film transistor.
2. Discussion of the Background
Active display devices such as liquid crystal displays (LCDs) and organic light emitting devices (OLEDs) include a plurality of pixels arranged in a matrix. Each pixel includes a field generating electrode and at least one transistor. The transistor may be a thin film transistor (TFT) having a semiconductor and three terminals such as a control terminal, an input terminal, and an output terminal. The thin film transistor transmits a data voltage in response to a gate signal or generates a current in proportion to the data voltage.
A display panel of the display devices may include a plurality of conductive layers and a plurality of insulating layers. The control electrode, the input and output electrodes, and the field generating electrode may be formed on the different conductive layers, respectively, and may be spaced apart from each other by the insulating layers.
When constructing the display panel, the thin film transistor may be manufactured in an inverse staggered bottom gate manner or a staggered top gate manner.
With a staggered top gate thin film transistor, the semiconductor is formed as the bottom layer, the input and output electrodes are formed on the semiconductor, and the gate electrode is formed as the top layer. The gate electrode overlaps the input and output electrodes as well as the semiconductor through the gate insulating layer.
However, near the edges of the input and output electrodes, the inclination distribution of the gate insulating layer may be different for each transistor and therefore, section shapes of the control electrodes may differ. When the section shapes of the control electrodes differ, an electric field generated by the gate electrodes may have a different shape, which may change the current amount driven by the transistors.
To prevent the above problems, the control electrodes may be designed such that the input and output electrodes do not overlap the control electrodes, and offset regions may be generated in semiconductor portions between the control electrodes and the input and output electrodes.
The display panel may be manufactured by an exposing process, an etching process, etc. When a mother substrate for manufacturing the display panel is larger than a predetermined size, the mother substrate may be divided into several regions and the exposing process may be sequentially performed for each region (partition exposure).
However, in the exposing process, an alignment error may occur due to shifting, rotation, or distortion of a mask. In addition, even when partition exposure is not performed, an alignment error may occur because of inaccuracies caused by the exposure equipment.
In particular, when the distance between the control electrode and the input electrode of the thin film transistor and the distance between the control electrode and the output electrode of the thin film transistor are different, the distances of the offset regions at the sides of the control electrodes are different, and therefore, the resistance of the offset regions and current amount based on the resistance may deviate.